Home Secretary John Reid is to tighten up the parole system in the wake of a series of revelations about released criminals.

A Home Office spokesman confirmed that "further strengthening" of rules governing inmates' release will go ahead.

On Tuesday night it emerged that 53 criminals have been freed despite being sentenced to life imprisonment within the last six years.

The parole system was already under scrutiny because of cases such as convicted rapist Anthony Rice, who murdered Naomi Bryant only nine months after being released from jail, and the murder of City financier John Monckton, killed by an offender who had been freed on licence.

The spokesman said, "The Home Secretary is reviewing parole arrangements and we believe that a further strengthening of the system will be necessary."

He was unable to say whether changes would be made to the way the Parole Board decides whether criminals should be freed, to the conditions imposed on offenders, or both.

Chancellor Gordon Brown backed the stance taken by Tony Blair and the Home Secretary during a visit to Blaenau Gwent. "I support what John Reid and the Prime Minister have said about this," he said. "We are concerned about the sentence.

"John Reid and the Prime Minister have made the views of the Government known on this."

He said there was "worry and anxiety that people are let out too early" among the public.

Liberal Democrat home affairs spokesman Nick Clegg said, "The fact that these offenders have been released into the community after only a few years in prison is a direct consequence of government policy."